Does fetal tracheal fluid flow during fetal breathing movements change before the onset of labour?

Abstract

Objective To examine changes in intra-tracheal fluid flow parameters during fetal breathing movements throughout the second half of pregnancy in the normally developing human fetus. Design Prospective cross-sectional study.Setting Fetal medicine unit at the Charité University Hospital in Berlin.Methods Assessment of tracheal fluid flow was attempted in 340 healthy fetuses (GA 20-40 weeks) in which fetal breathing movements were seen by B-mode scan. Colour Doppler was applied to visualise the tracheal fluid flow, followed by spectral Doppler to record the velocity waveforms. The records of 53 fetuses divided into five gestational age groups (20 -23, 24-27, 28-31, 32 -35 and 36 -40 weeks of gestation) containing 40 or more continuous breathing cycles (inspiration and expiration) were considered for analysis. Only regular breathing phases were examined and the volume obtained by integration of the tracheal fluid flow displaced during fetal breathing movements was calculated. Results The intra-tracheal flow volume moved during inspiration (Vi) and expiration (Ve) increased until 36 weeks of gestation after which there was a flattening until term. This suggests either a reduction of lung liquid production or a diminished lung liquid volume. The median difference between Vi and Ve was positive in the first four age groups and negative in the last one suggesting that, in mature fetuses, the effect of fetal breathing movements no longer results in an influx. Conclusions Our data demonstrate a modification in fetal behaviour that manifests itself during the last four weeks before birth and has the potential to reduce lung liquid volume.

Bacteria and endotoxin in meconium-stained amniotic fluid at term: could intra-amniotic infection cause meconium passage?

“…Does the fetus inhale amniotic fluid? Using ultrasound and color Doppler, the evidence is now clear that there is an influx and efflux of fluid not only in the nasopharynx and nose [254–259], but also in the trachea [259–261]. Fetal gasping was reported in humans by Boddy and Dawes, who describe gasping 24–72 hours before death in the absence of labor [262].…”

Surfactant Protein D in Newborn Infants: Factors Influencing Surfactant Protein D Levels in Umbilical Cord Blood and Capillary Blood

“…Uterine contractions have been reported to accelerate the secretion of pulmonary surfactant into the alveolar space and to decrease the amount of amniotic fluid by reabsorption of liquid across the pulmonary epithelium and outflow of liquid through the trachea (25)(26)(27)(28)(29). Three quarters of rat SP-D appears to exist in a soluble form, whereas 99% of rat SP-A exists in the form of a lipid protein complex (30).…”

Lung Pathology in Patients with Congenital Diaphragmatic Hernia Treated with Fetal Surgical Intervention, Including Tracheal Occlusion

“…Premature alveolar development is seen in this 13-day-old infant born at 28-wk gestation, treated with tracheal occlusion (Table 3, case 1). gest a halt in fluid influx after 36 wk, the age at which normal alveolarization begins [28]. This association raises the hypothesis that the dynamics of fluid exchange in the developing lung play a role in the timing of alveolarization.…”